Mechanical Properties of a Partially Solidified Cu-Zn Alloy
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CU-ZN alloys are used for water supply and drainage products. Because Cu-Zn alloys have a narrow solidification temperature range (freezing range), solidification cracking is rarely observed during casting compared with bronze. However, for dezincing-resistant brass with reduced lead, cracking is often found during shape casting. In recent years, the prediction of solidification cracking using computer-aided engineering (CAE) has gained particular interest. To predict solidification cracking, the fracture strength and fracture strain in the partially solidified state are essential. For example, Nagaumi and Umeda[1] obtained the fracture strain of Al-Mg-Si alloys using a partial solidification tensile test. The strain was compared with the results of thermal stress analysis to predict the solidification cracking of direct chill castings. Studies that used the partial solidification method are less numerous than studies that used the partial remelting method. For copper alloys, a few reports were found. Manabu Kiuchi[2] obtained the stress–strain curves using a compression test for both a Cu-35 pct Zn alloy and free cutting brass by the partial remelting method. However, in the partial remelting method, the NAOKI KASUYA and TOMOAKI NAKAZAWA, formerly M.S. Students with the Department of Mechanical Engineering, Graduate School of Waseda University, 3-4-1 Shinjuku-ku Okubo, Tokyo 1698555, Japan, are now Engineers with Toyota Motor Corporation, Toyota-cho 1, Toyota-shi, Aichi 471-8571, Japan. AKIRA MATSUSHITA, Ph.D. Student, is with the Department of Mechanical Engineering, Graduate School of Waseda University. Contact e-mail: [email protected] TOSHIMITSU OKANE, Leader, is with the Metal Processing Group, National Institute of Advanced Industrial Science and Technology, 1-1-1 Tsukuba Umezono, Ibaraki 305-8568, Japan. MAKOTO YOSHIDA, Professor, is with the Department of Mechanical Engineering, Graduate School of Waseda University, and also with the Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26 Shinjuku-ku Nishiwaseda, Tokyo 169-0051, Japan. Manuscript submitted June 10, 2015. Article published online February 3, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A
so-called melt back phenomenon should be inevitable. The micro-segregated part between dendrites is homogenized during the remelting process. In other words, the dendritic microstructure often tends to be lost. Zama et al.[3] reported that the remelting process reduces the concentration of magnesium between dendrites in an Al-Mg alloy. Differences in the mechanical properties between the two methods were also found. The ultimate tensile strength (UTS) and fracture strain obtained by the partial remelting method were lower than the partial solidification method regardless of the solid fraction. This shows that a tensile test with the partial solidification method should be used for the analysis of the solidification process. Oya et al.[4] measured tensile strength and apparent deformation of Cu-30 pct Zn, Cu-35
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